1. Field of the Invention
This invention relates to apparatus for conveying bags, and more particularly to apparatus for aligning an element of a bag conveying line with an edge of a tubular or semitubular plastic web.
2. Description of the Prior Art
In apparatus for the continuous production of plastic bags, welding stations that sever plastic bags closed by seam welds from tubular or semitubular plastic webs are usually followed by wicketer stacking stations, which include pairs of transfer arms that are provided with suction cups or other gripping means and are arranged to receive the cut bags and then to rotate through 180 degrees to transfer the cut bags onto respective pairs of stacking pins carried by an endless conveyor of a stacking conveyor line, whereby respective stacks of bags are formed on the conveyor. To permit the formation of stacks of several bags on the stacking lines, the bags are provided with suitable locating holes, which are punched into the continuous web before the wicketer stacking station. If the direction of travel of the web deviates laterally from the initial longitudinal direction of the web, the stacking operation will be disrupted because the individual bags which have been severed and provided with seam welds and locating holes cannot be carried over to the stacking conveyor in the correct position by the wicketer transfer arms, and the locating holes will not be properly positioned relative to the stacking pins on the stacking conveyor.
In order to ensure that the bags which have been severed and welded will be transferred by the wicketer transfer arms to the pairs of stacking pins in the proper position, it is known to displace the entire wicketer stacking station and the entire stacking conveyor line in a transverse direction to the extent of the measured deviation of the web so that the locating holes of the bags will receive the pairs of stacking pins. But the transverse displacement of the entire wicketer stacking station and the entire stacking conveyor line requires relatively expensive means and can be effected only slowly because large masses must be moved.
It is known from German Patent Specification No. 24 28 113 that a frame carrying a core for winding a web can be pivotally carried by an intermediate plate, which is guided on a base plate for a transverse displacement. In that arrangement, the frame is provided with drive mean for imparting a pivotal movement to the frame and the intermediate plate is provided with drive means for imparting a transverse movement to the intermediate plate. By means of sensors scanning an edge of the web the drive means can be so controlled that the edge of the web being wound on the core will be properly aligned.
It is an object of the present invention to permit a simpler and more rapid adjustment of the wicketer station and stacking conveyor line in response to a lateral deviation of the web.